[PATCH 19/20] mm/damon/reclaim: implement memory PSI-driven quota self-tuning

[SeongJae Park <sj@kernel.org>]

Support the PSI-driven quota self-tuning from DAMON_RECLAIM by
introducing yet another parameter, 'quota_mem_pressure_us'.  Users can
set the desired amount of memory pressure stall time per each quota
reset interval using the parameter.  Then DAMON_RECLAIM monitor the
memory pressure stall time, specifically system-wide memory 'some' PSI
value that increased during the given time interval, and self-tune the
quota using the DAMOS core logic.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/reclaim.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/mm/damon/reclaim.c b/mm/damon/reclaim.c
index 9df6b8819998..9bd341d62b4c 100644
--- a/mm/damon/reclaim.c
+++ b/mm/damon/reclaim.c
@@ -62,6 +62,21 @@ static struct damos_quota damon_reclaim_quota = {
 };
 DEFINE_DAMON_MODULES_DAMOS_QUOTAS(damon_reclaim_quota);
 
+/*
+ * Desired level of memory pressure-stall time in microseconds.
+ *
+ * While keeping the caps that set by other quotas, DAMON_RECLAIM automatically
+ * increases and decreases the effective level of the quota aiming this level of
+ * memory pressure is incurred.  System-wide ``some`` memory PSI in microseconds
+ * per quota reset interval (``quota_reset_interval_ms``) is collected and
+ * compared to this value to see if the aim is satisfied.  Value zero means
+ * disabling this auto-tuning feature.
+ *
+ * Disabled by default.
+ */
+static unsigned long quota_mem_pressure_us __read_mostly;
+module_param(quota_mem_pressure_us, ulong, 0600);
+
 /*
  * User-specifiable feedback for auto-tuning of the effective quota.
  *
@@ -198,6 +213,16 @@ static int damon_reclaim_apply_parameters(void)
 					&old_scheme->quota);
 	}
 
+	if (quota_mem_pressure_us) {
+		goal = damos_new_quota_goal(DAMOS_QUOTA_SOME_MEM_PSI_US,
+				quota_mem_pressure_us);
+		if (!goal) {
+			damon_destroy_scheme(scheme);
+			return -ENOMEM;
+		}
+		damos_add_quota_goal(&scheme->quota, goal);
+	}
+
 	if (quota_autotune_feedback) {
 		goal = damos_new_quota_goal(DAMOS_QUOTA_USER_INPUT, 10000);
 		if (!goal) {
-- 
2.39.2